It turns out that commit can cause problems for systems with multiple
GPUs, and causes X to hang on at least a HP Pavilion dv7 with hybrid
graphics.

This got noticed originally in 4.4.4, where this patch had already
gotten back-ported, but 4.5-rc7 was verified to have the same problem.

Alexander Deucher says:
"It looks like you have a muxed system so I suspect what's happening is
that one of the display is being reported as connected for both the
IGP and the dGPU and then the desktop environment gets confused or
there some sort problem in the detect functions since the mux is not
switched to the dGPU. I don't see an easy fix unless Dave has any
ideas. I'd say just revert for now"